Tetraaromatic diamine compounds as antioxidants

ABSTRACT

Tetraaromatic diamine compounds having the general formula: 
     
       
         
         
             
             
         
       
     
     are provided wherein a is 0-3; b, c and d independently are integers from 0-5, R 1  and R 2  together with the carbon atoms to which they are bonded are joined together to form a substituted or unsubstituted C 3  to about C 30  ring, saturated, partially unsaturated or fully unsaturated, optionally substituted with one or more heteroatoms, a is 0-3; b, c and d independently are integers from 0-5, R 3 , R 4 , R 5  and R 6  are independently hydrogen, a straight or branched C 1 -C 30  alkyl or alkylene group optionally substituted with one or more substituents, a substituted or unsubstituted C 3 -C 12  cycloalkyl, a substituted or unsubstituted C 5 -C 25  aryl, a substituted or unsubstituted C 6 -C 25  arylalkyl, a straight or branched C 1 -C 30  alkoxy group optionally substituted with one or more substituents or two R 4  substituents and/or two R 5  substituents and/or two R 6  substituents on adjacent carbon atoms of the aromatic ring associated therewith can be joined together to form a substituted or unsubstituted C 3  to about C 30  ring, saturated, partially unsaturated or fully unsaturated, optionally substituted with one or more heteroatoms. Lubricating oil compositions containing the tetraaromatic diamine compound additives are also provided.

PRIORITY

This application claims the benefit under 35 U.S.C. §119 to U.S.Provisional Application 60/802,975, filed on May 24, 2006, and entitled“TETRAAROMATIC DIAMINE COMPOUNDS AS ANTIOXIDANTS”, the contents of whichare incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention generally relates to additives for stabilizingorganic products that are subjected to oxidative, thermal, and/orlight-induced degradation. More particularly, the present inventionrelates to a class of tetraaromatic diamine compounds useful asantioxidants.

2. Description of the Related Art

The stabilization of organic materials with antioxidants or otherstabilizers are well known to those skilled in the art. For example, indeveloping lubricating oils, there have been many attempts to provideadditives that impart, for example, antioxidant, antiwear, and depositcontrol properties thereto. Zinc dialkyldithiophosphates (ZDDP) havebeen used as antifatigue, antiwear, antioxidant, extreme pressure andfriction modifying additives for lubricating oils for many years.However, they are subject to several drawbacks owing to their zinc andphosphorus contents. The presence of zinc contributes to the emission ofparticulates in the exhaust. In addition, during operation of aninternal combustion engine, lubricating oil enters the combustionchambers by means such as clinging to cylinder walls as the piston makesits down stroke.

When phosphorus-containing lubricating oil compositions enter thecombustion reaction, phosphorus enters the exhaust stream where it actsas a catalyst poison thus shortening the useful life of the catalyticconverter. However, zinc dialkyldithiophosphates give rise to ash, whichcontributes to particulate matter in automotive exhaust emissions, andregulatory agencies are seeking to reduce emissions of zinc into theenvironment. In addition, phosphorus, also a component of ZDDP, issuspected of limiting the service life of the catalytic converters thatare used on cars to reduce pollution. It is important to limit theparticulate matter and pollution formed during engine use fortoxicological and environmental reasons, but it is also important tomaintain undiminished the antioxidant properties of the lubricating oil.

In view of the aforementioned shortcomings of the known zinc andphosphorus-containing additives, efforts have been made to providelubricating oil additives that contain neither zinc nor phosphorus or,at least, contain them in substantially reduced amounts.

It would therefore be desirable to provide improved additives forstabilizing organic products that are subject to oxidative, thermal,and/or light-induced degradation and in need of stabilization to preventor inhibit such degradation, e.g., additives for lubricating oils thatcan improve the antioxidant properties of the oil while reducing thecontent of zinc and phosphorous of the lubricating oils.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, atetraaromatic diamine compound is provided having the general formula:

wherein a is 0-3; b, c and d independently are integers from 0-5; R¹ andR² together with the carbon atoms to which they are bonded are joinedtogether to form a substituted or unsubstituted C₃ to about C₃₀ ring,saturated, partially unsaturated or fully unsaturated, optionallysubstituted with one or more heteroatoms, R³, R⁴, R⁵ and R⁶ areindependently hydrogen, a straight or branched C₁-C₃₀ alkyl or alkylenegroup optionally substituted with one or more substituents, asubstituted or unsubstituted C₃-C₁₂ cycloalkyl, a substituted orunsubstituted C₅-C₂₅ aryl, a substituted or unsubstituted C₆-C₂₅arylalkyl, a straight or branched C₁-C₃₀ alkoxy group optionallysubstituted with one or more substituents or two R⁴ substituents and/ortwo R⁵ substituents and/or two R⁶ substituents on adjacent carbon atomsof the aromatic ring associated therewith can be joined together to forma substituted or unsubstituted C₃ to about C₃₀ ring, saturated,partially unsaturated or fully unsaturated, optionally substituted withone or more heteroatoms.

In accordance with a second embodiment of the present invention, alubricating oil composition is provided comprising (a) an oil oflubricating viscosity and (b) an antioxidant improving effective amountof at least one tetraaromatic diamine compound having the generalformula:

wherein R¹, R², R³, R⁴, R⁵, R⁶, a, b, c and d have the aforestatedmeanings.

In accordance with a third embodiment of the present invention, astabilizer-containing composition is provided comprising (a) an organicmaterial subject to oxidative, thermal, and/or light-induced degradationand in need of stabilization to prevent or inhibit such degradation; and(b) a stabilizing effective amount of at least one of at least onetetraaromatic diamine compound having the general formula:

wherein R¹, R², R³, R⁴, R⁵, R⁶, a, b, c and d have the aforestatedmeanings.

In accordance with a fourth embodiment of the present invention a methodfor stabilizing an organic material subject to oxidative, thermal,and/or light-induced degradation and in need of stabilization to preventor inhibit such degradation is provided, the method comprising adding tothe organic material a stabilizing effective amount of at least onetetraaromatic diamine compound having the general formula:

wherein R¹, R², R³, R⁴, R⁵, R⁶, a, b, c and d have the aforestatedmeanings.

The present invention advantageously provides tetraaromatic diaminecompound additives and lubricating oil compositions which providedeposit protection in addition to oxidation-corrosion protection. Thelubricating oil compositions can also provide such protection whilehaving relatively low levels of phosphorous, i.e., less than about 0.1%,preferably less than about 0.08% and more preferably less than about0.05% by weight. Accordingly, the lubricating oil compositions of thepresent invention can be more environmentally desirable than the higherphosphorous lubricating oil compositions generally used in internalcombustion engines because they facilitate longer catalytic converterlife and activity while also providing the desired high depositprotection. This is believed to be due to the substantial absence ofadditives containing phosphorus compounds in these lubricating oilcompositions. The tetraaromatic diamine compound additives of thisinvention may also protect against oxidation both in the presence oftransition metals such as, for example, iron (Fe) and Copper (Cu), etc.,as well as in a metal free environment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The tetraaromatic diamine compounds, useful as antioxidants, of thepresent invention are represented by the general formula 1:

wherein a is 0-3; b, c and d independently are integers from 0-5; R¹ andR² together with the carbon atoms to which they are bonded are joinedtogether to form a substituted or unsubstituted C₃ to about C₃₀ ring,saturated, partially unsaturated or fully unsaturated, optionallysubstituted with one or more heteroatoms, including, by way of example,ring structures such as a phenyl ring (to form a naphthalene ringstructure with the phenyl ring to which it is attached), cyclopentyl,cyclohexyl (to form a tetralin ring structure with the phenyl ring towhich it is attached), optionally substituted with one or moresubstituents; R³, R⁴, R⁵ and R⁶ are independently hydrogen, a straightor branched C₁-C₃₀ alkyl or alkylene group optionally substituted withone or more substituents, a substituted or unsubstituted C₃-C₁₂cycloalkyl, a substituted or unsubstituted C₅-C₂₅ aryl, a substituted orunsubstituted C₆-C₂₅ arylalkyl, a straight or branched C₁-C₃₀ alkoxygroup optionally substituted with one or more substituents, or two R⁴substituents and/or two R⁵ substituents and/or two R⁶ substituents onadjacent carbon atoms of the aromatic ring associated therewith can bejoined together to form a substituted or unsubstituted C₃ to about C₃₀ring, saturated, partially unsaturated or fully unsaturated, optionallysubstituted with one or more heteroatoms including, by way of example,the ring structures discussed above.

Representative examples of heteroatoms for use herein include, by way ofexample, O, S, N and the like and combinations thereof.

Representative examples of alkyl groups for use herein include, by wayof example, a straight or branched hydrocarbon chain radical containingcarbon and hydrogen atoms of from 1 to about 30 carbon atoms with orwithout unsaturation, to the rest of the molecule, e.g., methyl, ethyl,n-propyl, 1-methylethyl (isopropyl), n-butyl, n-pentyl, etc., and thelike.

Representative examples of cycloalkyl groups for use herein include, byway of example, a substituted or unsubstituted non-aromatic mono ormulticyclic ring system of about 3 to about 12 carbon atoms such as, forexample, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, optionallycontaining one or more heteroatoms.

Representative examples of aryl groups for use herein include, by way ofexample, a substituted or unsubstituted monoaromatic or polyaromaticradical containing from about 5 to about 25 carbon atoms such as, forexample, phenyl, naphthyl, and the like, optionally containing one ormore heteroatoms.

Representative examples of arylalkyl groups for use herein include, byway of example, a substituted or unsubstituted aryl group as definedabove directly bonded to an alkyl group as defined above which is thenattached to the main structure of the monomer at any carbon atom fromthe alkyl group that results in the creation of a stable structure,e.g., —CH₂C₆H₅, —C₂H₄C₆H₅ and the like, wherein the aryl group canoptionally contain one or more heteroatoms.

Representative examples of alkoxy groups for use herein include, by wayof example, a hydrocarbon group such as the alkyl, cycloalkyl, aryl, andarylalkyl as defined above attached via oxygen linkage to the rest ofthe molecule, i.e., of the general formula —OR⁸, wherein R⁸ is an alkyl,cycloalkyl, cycloalkylalkyl, cycloalkenyl, aryl or an arylalkyl group asdefined above, e.g., —OCH₃, —OC₂H₅, or —OC₆H₅, and the like.

The substituents in the ‘substituted alkyl’, ‘substituted cycloalkyl’,‘substituted aryl’, substituted arylalkyl’, and ‘substituted alkoxy’ maybe the same or different and include one or more substituents such ashydrogen, hydroxy, halogen, carboxyl, cyano, nitro, oxo (═O), thio (═S),substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy,substituted or unsubstituted alkenyl, substituted or unsubstitutedalkynyl, substituted or unsubstituted aryl, substituted or unsubstitutedarylalkyl, substituted or unsubstituted cycloalkyl, substituted orunsubstituted cycloalkenyl, substituted or unsubstituted amino,substituted or unsubstituted aryl, substituted or unsubstitutedheteroaryl, substituted heterocycloalkyl ring, substituted orunsubstituted heteroarylalkyl, substituted or unsubstituted heterocyclicring, —COOR_(x), —C(O)R_(x), —C(S)R_(x), —C(O)NR_(x)R_(y),—C(O)ONR_(x)R_(y), —NR_(x)CONR_(y)R_(z), —N(R_(x))SOR_(y),—N(R_(x))SO₂R_(y), —(═N—N(Rx)R_(y)), —NR_(x)C(O)OR_(y), —NR_(x)R_(y),—NR_(x)C(O)R_(y)—, —NR_(x)C(S)R_(y) —NR_(x)C(S)NR_(y)R_(z),—SONR_(x)R_(y)—, —SO₂NR_(x)R_(y)—, —OR_(x), —OR_(x)C(O)NR_(y)R_(z),—OR_(x)C(O)OR_(y)—, —OC(O)R_(x), —OC(O)NR_(x)R_(y),—R_(x)NR_(y)C(O)R_(z), —R_(x)OR_(y), —R_(x)C(O)OR_(y),—R_(x)C(O)NR_(y)R_(z), —R_(x)C(O)R_(x), —R_(x)OC(O)R_(y), —SR_(x),—SOR_(x), —SO₂R_(x), —ONO₂, wherein R_(x), R_(y) and R_(z) in each ofthe above groups can be the same or different and can be a hydrogenatom, substituted or unsubstituted alkyl, substituted or unsubstitutedalkoxy, substituted or unsubstituted alkenyl, substituted orunsubstituted alkynyl, substituted or unsubstituted aryl, substituted orunsubstituted arylalkyl, substituted or unsubstituted cycloalkyl,substituted or unsubstituted cycloalkenyl, substituted or unsubstitutedamino, substituted or unsubstituted aryl, substituted or unsubstitutedheteroaryl, ‘substituted heterocycloalkyl ring’ substituted orunsubstituted heteroarylalkyl, or a substituted or unsubstitutedheterocyclic ring.

In one embodiment, the tetraaromatic diamine compounds of this inventioncan be where R¹ and R² are joined together to form a substituted orunsubstituted, saturated or partially or fully unsaturated 5-, 6-, or7-membered ring optionally substituted with one or more heteroatoms. Inanother embodiment, the tetraaromatic diamine compounds of thisinvention can be where two R⁴ substituents and/or two R⁵ substituentsand/or two R⁶ substituents on adjacent carbon atoms of the aromatic ringassociated therewith are joined together to form a substituted orunsubstituted, saturated or partially or fully unsaturated C₃ to aboutC₃₀ ring optionally substituted with one or more heteroatoms. In yetanother embodiment, the tetraaromatic diamine compounds of thisinvention can be where two R⁴ substituents and/or two R⁵ substituentsand/or two R⁶ substituents on adjacent carbon atoms of the aromatic ringassociated therewith are joined together to form a substituted orunsubstituted, unsaturated, saturated or partially or fully unsaturated5-, 6-, or 7-membered ring optionally substituted with one or moreheteroatoms. In still yet another embodiment, the tetraaromatic diaminecompounds of this invention can be where R¹ and R² are joined togetherto form a substituted or unsubstituted and saturated or partially orfully unsaturated 5-, 6-, or 7-membered ring optionally substituted withone or more heteroatoms and two R⁴ substituents and/or two R⁵substituents and/or two R⁶ substituents on adjacent carbon atoms of thearomatic ring associated therewith are joined together to form asubstituted or unsubstituted and saturated or partially or fullyunsaturated 5-, 6-, or 7-membered ring optionally substituted with oneor more heteroatoms.

The tetraaromatic diamine compounds of this invention can be obtained bythe oxidation of the corresponding substituted diphenyl amines with anoxidizing agent under suitable reaction conditions to form the compoundsherein. Useful oxidizing agents include, but are not limited to,Na₂Cr₂O₇/AcOH or KMnO₄, PbO₂, AgO, tert-butyl peroxide and the like. Thetemperature for this reaction will ordinarily range from about 10° C. toabout 80° C. and more preferably from about 20° C. to about 40° C. Ifdesired, the reaction can be carried out in a suitable solvent. Suitablesolvents include, but are not limited to, aliphatic hydrocarbons, e.g.,hexane and the like; aromatic hydrocarbons, e.g., toluene, xylene,benzene and the like; ketones, e.g., acetone and the like; halogenatedhydrocarbons, e.g., dichloromethane, chloroform, and the like andmixtures thereof.

The tetraaromatic diamine compounds of this invention may have usefulantioxidant properties for use as antioxidants in, for example,compounded tires, polyols, plastics, urethanes, greases, motor oils,rubber belts, cables, gaskets, seals, rubber products in the garment andcarpet industries. Accordingly, an embodiment of the present inventionis a stabilizer-containing composition containing an organic materialsubject to oxidative, thermal, and/or light-induced degradation and inneed of stabilization to prevent or inhibit such degradation and, as astabilizer therefore, the foregoing tetraaromatic diamine compounds. Thetetraaromatic diamine compound stabilizers can be added to the organicmaterial in an amount sufficient to impart an appreciable stabilizingeffect. In general, this amount may vary from about 0.1 wt. % to about 5wt. % weight percent, preferably from about 0.5 wt. % to about 3 wt. %weight percent and more preferably from about 0.5 wt. % to about 2.0 wt.% by total weight of the organic material.

Another embodiment of the present invention is a lubricating oilcomposition containing at least (a) an oil of lubricating viscosity and(b) an effective amount of at least one of the foregoing tetraaromaticdiamine compounds. Generally, the oil of lubricating viscosity for usein the lubricating oil compositions may be present in a major amount,e.g., an amount of greater than about 50 wt. %, preferably greater thanabout 70 wt. %, more preferably from about 80 to about 99.5 wt. % andmost preferably from about 85 to about 98 wt. %, based on the totalweight of the composition. The oil of lubricating viscosity for useherein can be any presently known or later-discovered oil of lubricatingviscosity used in formulating lubricating oil compositions for any andall such applications, e.g., engine oils, marine cylinder oils,functional fluids such as hydraulic oils, gear oils, transmissionfluids, e.g., automatic transmission fluids, etc. turbine lubricants,compressor lubricants, metal-working lubricants, and other lubricatingoil and grease compositions. Additionally, the oil of lubricatingviscosity for use herein can optionally contain viscosity indeximprovers, e.g., polymeric alkylmethacrylates; olefinic copolymers,e.g., an ethylene-propylene copolymer or a styrene-butadiene copolymer;and the like and mixtures thereof.

As one skilled in the art would readily appreciate, the viscosity of theoil of lubricating viscosity is dependent upon the application.Accordingly, the viscosity of an oil of lubricating viscosity for useherein will ordinarily range from about 2 to about 2000 centistokes(cSt) at 100° Centigrade (C). Generally, individually the oils used asengine oils will have a kinematic viscosity range at 100° C. of about 2cSt to about 30 cSt, preferably about 3 cSt to about 16 cSt, and mostpreferably about 4 cSt to about 12 cSt and will be selected or blendeddepending on the desired end use and the additives in the finished oilto give the desired grade of engine oil, e.g., a lubricating oilcomposition having an SAE Viscosity Grade of 0W, 0W-20, 0W-30, 0W-40,0W-50, 0W-60, 5W, 5W-20, 5W-30, 5W-40, 5W-50, 5W-60, 10W, 10W-20,10W-30, 10W-40, 10W-50, 15W, 15W-20, 15W-30 or 15W-40. Oils used as gearoils can have viscosities ranging from about 2 cSt to about 2000 cSt at100° C.

Base stocks may be manufactured using a variety of different processesincluding, but not limited to, distillation, solvent refining, hydrogenprocessing, oligomerization, esterification, and rerefining. Rerefinedstock shall be substantially free from materials introduced throughmanufacturing, contamination, or previous use. The base oil of thelubricating oil compositions of this invention may be any natural orsynthetic lubricating base oil. Suitable hydrocarbon synthetic oilsinclude, but are not limited to, oils prepared from the polymerizationof ethylene or from the polymerization of 1-olefins to provide polymerssuch as polyalphaolefin or PAO oils, or from hydrocarbon synthesisprocedures using carbon monoxide and hydrogen gases such as in aFisher-Tropsch process. For example, a suitable oil of lubricatingviscosity is one that comprises little, if any, heavy fraction; e.g.,little, if any, lube oil fraction of viscosity about 20 cSt or higher at100° C.

The oil of lubricating viscosity may be derived from natural lubricatingoils, synthetic lubricating oils or mixtures thereof. Suitable oilsincludes base stocks obtained by isomerization of synthetic wax andslack wax, as well as hydrocracked base stocks produced by hydrocracking(rather than solvent extracting) the aromatic and polar components ofthe crude. Suitable oils include those in all API categories I, II, III,IV and V as defined in API Publication 1509, 14th Edition, Addendum I,December 1998. Group IV base oils are polyalphaolefins (PAO). Group Vbase oils include all other base oils not included in Group I, II, III,or IV. Although Group II, III and IV base oils are preferred for use inthis invention, these preferred base oils may be prepared by combiningone or more of Group I, II, III, IV and V base stocks or base oils.

Useful natural oils include mineral lubricating oils such as, forexample, liquid petroleum oils, solvent-treated or acid-treated minerallubricating oils of the paraffinic, naphthenic or mixedparaffinic-naphthenic types, oils derived from coal or shale, animaloils, vegetable oils (e.g., rapeseed oils, castor oils and lard oil),and the like.

Useful synthetic lubricating oils include, but are not limited to,hydrocarbon oils and halo-substituted hydrocarbon oils such aspolymerized and interpolymerized olefins, e.g., polybutylenes,polypropylenes, propylene-isobutylene copolymers, chlorinatedpolybutylenes, poly(1-hexenes), poly(1-octenes), poly(1-decenes), andthe like and mixtures thereof; alkylbenzenes such as dodecylbenzenes,tetradecylbenzenes, dinonylbenzenes, di(2-ethylhexyl)-benzenes, and thelike; polyphenyls such as biphenyls, terphenyls, alkylated polyphenyls,and the like; alkylated diphenyl ethers and alkylated diphenyl sulfidesand their derivative, analogs and homologs thereof and the like.

Other useful synthetic lubricating oils include, but are not limited to,oils made by polymerizing olefins of less than 5 carbon atoms such asethylene, propylene, butylenes, isobutene, pentene, and mixturesthereof. Methods of preparing such polymer oils are well known to thoseskilled in the art.

Additional useful synthetic hydrocarbon oils include liquid polymers ofalpha olefins having the proper viscosity. Especially useful synthetichydrocarbon oils are the hydrogenated liquid oligomers of C₆ to C₁₂alpha olefins such as, for example, 1-decene trimer.

Another class of useful synthetic lubricating oils includes, but is notlimited to, alkylene oxide polymers, i.e., homopolymers, interpolymers,and derivatives thereof where the terminal hydroxyl groups have beenmodified by, for example, esterification or etherification. These oilsare exemplified by the oils prepared through polymerization of ethyleneoxide or propylene oxide, the alkyl and phenyl ethers of thesepolyoxyalkylene polymers (e.g., methyl poly propylene glycol etherhaving an average molecular weight of about 1,000, diphenyl ether ofpolyethylene glycol having a molecular weight of about 500 to about1000, diethyl ether of polypropylene glycol having a molecular weight ofabout 1,000 to about 1,500, etc.) or mono- and polycarboxylic estersthereof such as, for example, the acetic esters, mixed C₃-C₈ fatty acidesters, or the C₁₃oxo acid diester of tetraethylene glycol.

Yet another class of useful synthetic lubricating oils include, but arenot limited to, the esters of dicarboxylic acids e.g., phthalic acid,succinic acid, alkyl succinic acids, alkenyl succinic acids, maleicacid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipicacid, linoleic acid dimer, malonic acids, alkyl malonic acids, alkenylmalonic acids, etc., with a variety of alcohols, e.g., butyl alcohol,hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol,diethylene glycol monoether, propylene glycol, etc. Specific examples ofthese esters include dibutyl adipate, di(2-ethylhexyl)sebacate,di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecylazelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the2-ethylhexyl diester of linoleic acid dimer, the complex ester formed byreacting one mole of sebacic acid with two moles of tetraethylene glycoland two moles of 2-ethylhexanoic acid and the like.

Esters useful as synthetic oils also include, but are not limited to,those made from carboxylic acids having from about 5 to about 12 carbonatoms with alcohols, e.g., methanol, ethanol, etc., polyols and polyolethers such as neopentyl glycol, trimethylol propane, pentaerythritol,dipentaerythritol, tripentaerythritol, and the like.

Silicon-based oils such as, for example, polyalkyl-, polyaryl-,polyalkoxy- or polyaryloxy-siloxane oils and silicate oils, compriseanother useful class of synthetic lubricating oils. Specific examples ofthese include, but are not limited to, tetraethyl silicate,tetra-isopropyl silicate, tetra-(2-ethylhexyl)silicate,tetra-(4-methyl-hexyl)silicate, tetra-(p-tert-butylphenyl)silicate,hexyl-(4-methyl-2-pentoxy)disiloxane, poly(methyl)siloxanes,poly(methylphenyl)siloxanes, and the like. Still yet other usefulsynthetic lubricating oils include, but are not limited to, liquidesters of phosphorous containing acids, e.g., tricresyl phosphate,trioctyl phosphate, diethyl ester of decane phosphionic acid, etc.,polymeric tetrahydrofurans and the like.

The oil of lubricating viscosity may be derived from unrefined, refinedand rerefined oils, either natural, synthetic or mixtures of two or moreof any of these of the type disclosed hereinabove. Unrefined oils arethose obtained directly from a natural or synthetic source (e.g., coal,shale, or tar sands bitumen) without further purification or treatment.Examples of unrefined oils include, but are not limited to, a shale oilobtained directly from retorting operations, a petroleum oil obtaineddirectly from distillation or an ester oil obtained directly from anesterification process, each of which is then used without furthertreatment. Refined oils are similar to the unrefined oils except theyhave been further treated in one or more purification steps to improveone or more properties. These purification techniques are known to thoseof skill in the art and include, for example, solvent extractions,secondary distillation, acid or base extraction, filtration,percolation, hydrotreating, dewaxing, etc. Rerefined oils are obtainedby treating used oils in processes similar to those used to obtainrefined oils. Such rerefined oils are also known as reclaimed orreprocessed oils and often are additionally processed by techniquesdirected to removal of spent additives and oil breakdown products.

Lubricating oil base stocks derived from the hydroisomerization of waxmay also be used, either alone or in combination with the aforesaidnatural and/or synthetic base stocks. Such wax isomerate oil is producedby the hydroisomerization of natural or synthetic waxes or mixturesthereof over a hydroisomerization catalyst.

Natural waxes are typically the slack waxes recovered by the solventdewaxing of mineral oils; synthetic waxes are typically the wax producedby the Fischer-Tropsch process.

The tetraaromatic diamine compound additives of this invention can beused as a complete or partial replacement for commercially availableantioxidants currently used in lubricant formulations and can be incombination with other additives typically found in motor oils andfuels. When used in combination with other types of antioxidants oradditives used in oil formulations, synergistic and/or additiveperformance effects may also be obtained with respect to improvedantioxidancy, antiwear, frictional and detergency and high temperatureengine deposit properties. Such other additives can be any presentlyknown or later-discovered additives used in formulating lubricating oilcompositions. The lubricating oil additives typically found inlubricating oils are, for example, dispersants, detergents,corrosion/rust inhibitors, antioxidants, anti-wear agents,anti-foamants, friction modifiers, seal swell agents, emulsifiers, VIimprovers, pour point depressants, and the like. See, for example, U.S.Pat. No. 5,498,809 for a description of useful lubricating oilcomposition additives, the disclosure of which is incorporated herein byreference in its entirety.

Examples of dispersants include polyisobutylene succinimides,polyisobutylene succinate esters, Mannich Base ashless dispersants, andthe like. Examples of detergents include metallic and ashless alkylphenates, metallic and ashless sulfurized alkyl phenates, metallic andashless alkyl sulfonates, metallic and ashless alkyl salicylates,metallic and ashless saligenin derivatives, and the like.

Examples of other antioxidants include alkylated diphenylamines,N-alkylated phenylenediamines, phenyl-naphthylamine, alkylatedphenyl-naphthylamine, dimethyl quinolines, trimethyldihydroquinolinesand oligomeric compositions derived therefrom, hindered phenolics,alkylated hydroquinones, hydroxylated thiodiphenyl ethers,alkylidenebisphenols, thiopropionates, metallic dithiocarbamates,1,3,4-dimercaptothiadiazole and derivatives, oil soluble coppercompounds, and the like. Representative examples of such additives arethose commercially available from such sources as Chemtura Corporationand include, for example, Naugalube® 438, Naugalube 438L, Naugalube 640,Naugalube 635, Naugalube 680, Naugalube AMS, Naugalube APAN, NaugardPANA, Naugalube TMQ, Naugalube 531, Naugalube 431, Naugard® BHT,Naugalube 403, Naugalube 420 and the like.

Examples of anti-wear additives that can be used in combination with theadditives of the present invention include organo borates, organophosphites, organo phosphates, organic sulfur-containing compounds,sulfurized olefins, sulfurized fatty acid derivatives (esters),chlorinated paraffins, zinc dialkyldithiophosphates, zincdiaryldithiophosphates, dialkyldithiophosphate esters, diaryldithiophosphate esters, phosphosulfurized hydrocarbons, and the like.Representative examples of such additives are those commerciallyavailable from The Lubrizol Corporation such as Lubrizol 677A, Lubrizol1095, Lubrizol 1097, Lubrizol 1360, Lubrizol 1395, Lubrizol 5139,Lubrizol 5604 and the like, and from Ciba Corporation such as Irgalube353 and the like.

Examples of friction modifiers include fatty acid esters and amides,organo molybdenum compounds, molybdenum dialkyldithiocarbamates,molybdenum dialkyl dithiophosphates, molybdenum disulfide,tri-molybdenum cluster dialkyldithiocarbamates, non-sulfur molybdenumcompounds and the like. Representative examples of such frictionmodifiers are those commercially available from R.T. Vanderbilt Company,Inc. such as Molyvan A, Molyvan L, Molyvan 807, Molyvan 856B, Molyvan822, Molyvan 855, and the like; Asahi Denka Kogyo K.K. such asSAKURA-LUBE 100, SAKURA-LUBE 165, SAKURA-LUBE 300, SAKURA-LUBE 310G,SAKURA-LUBE 321, SAKURA-LUBE 474, SAKURA-LUBE 600, SAKURA-LUBE 700, andthe like; and from Akzo Nobel Chemicals GmbH such as Ketjen-Ox 77M,Ketjen-Ox 77TS, and the like.

An example of an anti-foam agent is polysiloxane, and the like. Examplesof rust inhibitors are polyoxyalkylene polyol, benzotriazolederivatives, and the like. Examples of VI improvers include olefincopolymers and dispersant olefin copolymers, and the like. An example ofa pour point depressant is polymethacrylate, and the like.

As noted above, suitable anti-wear compounds include dihydrocarbyldithiophosphates. Preferably, the hydrocarbyl groups contain an averageof at least 3 carbon atoms. Particularly useful are metal salts of atleast one dihydrocarbyl dithiophosphoric acid wherein the hydrocarbylgroups contain an average of at least 3 carbon atoms. The acids fromwhich the dihydrocarbyl dithiophosphates can be derived can beillustrated by acids of the formula:

wherein R¹¹ and R¹² are the same or different and can be linear orbranched alkyl, cycloalkyl, aralkyl, alkaryl, or substitutedsubstantially hydrocarbyl radical derivatives of any of the abovegroups, and wherein the R¹¹ and R¹² groups in the acid each have, onaverage, at least 3 carbon atoms. By “substantially hydrocarbyl” ismeant radicals containing substituent groups, e.g., 1 to 4 substituentgroups per radical moiety such as, for example, ether, ester, thio,nitro, or halogen, that do not materially affect the hydrocarboncharacter of the radical.

Specific examples of suitable R¹¹ and R¹² radicals include isopropyl,isobutyl, n-butyl, sec-butyl, n-hexyl, heptyl, 2-ethylhexyl, diisobutyl,isooctyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, butylphenyl,o,p-dipentylphenyl, octylphenyl, polyisobutene-(molecular weight350)-substituted phenyl, tetrapropylene-substituted phenyl,beta-octylbutylnaphthyl, cyclopentyl, cyclohexyl, phenyl, chlorophenyl,o-dichlorophenyl, bromophenyl, naphthenyl, 2-methylcyclohexyl, benzyl,chlorobenzyl, chloropentyl, dichlorophenyl, nitrophenyl, dichlorodecyland xenyl radicals. Alkyl radicals having from about 3 to about 30carbon atoms and aryl radicals having from about 6 to about 30 carbonatoms are preferred. Particularly preferred R¹¹ and R¹² radicals arealkyl of from 4 to about 18 carbon atoms.

The phosphorodithioic acids are readily obtainable by the reaction of aphosphorus pentasulfide and an aliphatic alcohol and/or phenol. Thereaction involves at least mixing, at a temperature ranging from about20° C. to 200° C., about 4 moles of the alcohol or phenol with one moleof phosphorus pentasulfide. Hydrogen sulfide can be liberated as thereaction takes place. Mixtures of alcohols, phenols, or both can beemployed, e.g., mixtures of C₃ to C₃₀ alcohols, C₆ to C₃₀ aromaticalcohols, etc. The metals useful to make the phosphate salts include,but are not limited to, Group I metals, Group II metals, aluminum, lead,tin, molybdenum, manganese, cobalt, and nickel with zinc being thepreferred metal. Examples of metal compounds that can be reacted withthe acid include lithium oxide, lithium hydroxide, lithium carbonate,lithium pentylate, sodium oxide, sodium hydroxide, sodium carbonate,sodium methylate, sodium propylate, sodium phenoxide, potassium oxide,potassium hydroxide, potassium carbonate, potassium methylate, silveroxide, silver carbonate, magnesium oxide, magnesium hydroxide, magnesiumcarbonate, magnesium ethylate, magnesium propylate, magnesium phenoxide,calcium oxide, calcium hydroxide, calcium carbonate, calcium methylate,calcium propylate, calcium pentylate, zinc oxide, zinc hydroxide, zinccarbonate, zinc propylate, strontium oxide, strontium hydroxide, cadmiumoxide, cadmium hydroxide, cadmium carbonate, cadmium ethylate, bariumoxide, barium hydroxide, barium hydrate, barium carbonate, bariumethylate, barium pentylate, aluminum oxide, aluminum propylate, leadoxide, lead hydroxide, lead carbonate, tin oxide, tin butylate, cobaltoxide, cobalt hydroxide, cobalt carbonate, cobalt pentylate, nickeloxide, nickel hydroxide, nickel carbonate and the like and mixturesthereof.

In some instances, the incorporation of certain ingredients,particularly carboxylic acids or metal carboxylates, e.g., small amountsof the metal acetate or acetic acid, used in conjunction with the metalreactant will facilitate the reaction and result in an improved product.For example, the use of up to about 5% of zinc acetate in combinationwith the required amount of zinc oxide facilitates the formation of azinc phosphorodithioate.

The preparation of metal phosphorodithioates is well known in the art.See, e.g., U.S. Pat. Nos. 3,293,181; 3,397,145; 3,396,109; and3,442,804; the disclosures of which are hereby incorporated byreference. Also useful as anti-wear additives are amine derivatives ofdithiophosphoric acid compounds, such as are described in U.S. Pat. No.3,637,499, the disclosure of which is hereby incorporated by referencein its entirety.

The zinc salts are most commonly used as anti-wear additives inlubricating oils in amounts ranging from about 0.1 to about 10,preferably about 0.2 to about 2 wt. %, based upon the total weight ofthe lubricating oil composition. They may be prepared in accordance withknown techniques, e.g., by first forming a dithiophosphoric acid,usually by reaction of an alcohol and/or a phenol with P₂S₅ and thenneutralizing the dithiophosphoric acid with a suitable zinc compound.

Mixtures of alcohols can be used, including mixtures of primary andsecondary alcohols, secondary generally for imparting improved antiwearproperties and primary for thermal stability. In general, any basic orneutral zinc compound could be used, but the oxides, hydroxides, andcarbonates are most generally employed. Commercial additives frequentlycontain an excess of zinc owing to use of an excess of the basic zinccompound in the neutralization reaction.

The zinc dihydrocarbyl dithiophosphates (ZDDP) are oil soluble salts ofdihydrocarbyl esters of dithiophosphoric acids and can be represented bythe following formula:

wherein R¹¹ and R¹² have the aforestated meanings.

The lubricating oil compositions of the present invention, when theycontain these additives, are typically blended into a base oil inamounts such that the additives therein are effective to provide theirnormal attendant functions. Representative effective amounts of suchadditives are illustrated in Table 1.

TABLE 1 More Additives Preferred Weight % Preferred Weight % V.I.Improver about 1 to about 12 about 1 to about 4 Corrosion Inhibitorabout 0.01 to about 3 about 0.01 to about 1.5 Oxidation Inhibitor about0.01 to about 5 about 0.01 to about 1.5 Dispersant about 0.1 to about 10about 0.1 to about 5 Lube Oil Flow about 0.01 to about 2 about 0.01 toabout 1.5 Improver Detergent/Rust about 0.01 to about 6 about 0.01 toabout 3 Inhibitor Pour Point about 0.01 to about 1.5 about 0.01 to about0.5 Depressant Anti-foaming about 0.001 to about 0.1 about 0.001 toabout 0.01 Agents Anti-wear Agents about 0.001 to about 5 about 0.001 toabout 1.5 Seal Swell Agents about 0.1 to about 8 about 0.1 to about 4Friction Modifiers about 0.01 to about 3 about 0.01 to about 1.5Lubricating Base Balance Balance Oil

When other additives are employed, it may be desirable, although notnecessary, to prepare additive concentrates comprising concentratedsolutions or dispersions of the tetraaromatic diamine compound additivesof this invention (in concentrate amounts hereinabove described),together with one or more other additives (the concentrate whenconstituting an additive mixture being referred to herein as anadditive-package) whereby several additives can be added simultaneouslyto the base oil to form the lubricating oil composition. Dissolution ofthe additive concentrate into the lubricating oil can be facilitated by,for example, solvents and by mixing accompanied by mild heating, butthis is not essential.

The concentrate or additive-package will typically be formulated tocontain the additives in proper amounts to provide the desiredconcentration in the final formulation when the additive-package iscombined with a predetermined amount of base lubricant. Thus, thesubject additives of the present invention can be added to small amountsof base oil or other compatible solvents along with other desirableadditives to form additive-packages containing active ingredients incollective amounts of, typically, from about 2.5 to about 90 percent,preferably from about 15 to about 75 percent, and more preferably fromabout 25 percent to about 60 percent by weight additives in theappropriate proportions with the remainder being base oil. The finalformulations can typically employ about 1 to 20 weight percent of theadditive-package with the remainder being base oil.

All of the weight percentages expressed herein (unless otherwiseindicated) are based on the active ingredient (Al) content of theadditive, and/or upon the total weight of any additive-package, orformulation, which will be the sum of the Al weight of each additiveplus the weight of total oil or diluent.

In general, the lubricant compositions of the invention contain theadditives in a concentration ranging from about 0.05 to about 30 weightpercent. A concentration range for the additives ranging from about 0.1to about 10 weight percent based on the total weight of the oilcomposition is preferred. A more preferred concentration range is fromabout 0.2 to about 5 weight percent. Oil concentrates of the additivescan contain from about 1 to about 75 weight percent of the additive in acarrier or diluent oil of lubricating oil viscosity.

The following non-limiting examples are illustrative of the presentinvention.

EXAMPLE 1

This example illustrates the preparation of a compound of the formula.

Bromination

To a well stirred mixture of tetralin (360 g, 2.7 mol) and iodine (1 g)cooled in an ice bath was slowly added bromine (470 g, 2.9 mol) over a 3hour period maintaining an internal temperature of 0-10° C. (note:vigorous evolution of HBr quenched by sodium hydroxide scrubber). Themixture was left to warm to room temperature and stirred overnight. Themixture was then poured into a cooled (5° C.) saturated solution (1.5liters) of sodium sulfite, stirred for 40 minutes and extracted withCH₂Cl₂ twice (500 mL, 200 mL). The combined extracts were dried oversodium sulfate and concentrated on a rotovap. The residue was distilledunder vacuum. A forerun of mostly starting material was collected up to760° C. at 1.3-0.58 T. The product was distilled at 73-86° C. at0.3-0.6T as a mixture of isomers (collected in several fractions for atotal of ˜450 g).

Coupling

A mixture of the 2-aminoindan (39.8 g, 0.30 mol), tetralin bromide (65g, 0.30 mol) and 50% NaOH (22 mL) in toluene (220 mL) was purged withnitrogen for 45 minutes. Bis(tri-t-butylphosphine)palladium(0) (0.8 g,0.0016 mol) and cetyltrimethylammonium bromide (0.28 g, 0.0008 mol) wereadded to the flask under a stream of nitrogen. The mixture was thenheated at about 100° C. for 16 hours. TLC analysis indicated littlereaction so another portion of catalyst (0.8 g) and phase-transfer agent(0.28 g) was added and the reaction was continued. After an additional 4hours, TLC indicated about 80% conversion. The mixture was heated for anadditional 3 days and then left to cool overnight without stirring. Themixture was filtered through Celite and the filter cake rinsed withtoluene. The solution was extracted with water (100 mL) and concentratedon a rotovap. The resulting residue was distilled on a short-pathKugelrohr apparatus with a vacuum. A forerun fraction was collected upto 140° C. at 0.89 T. After further heating to 160° C. (at 0.6-3.6 T),the product (73 g) was distilled as a yellow oil which solidified onstanding. GC/FID analysis indicated a purity of 98.7% (by area %) and a3:1 ratio of the two isomeric products. This reaction is generally shownbelow in Scheme I.

EXAMPLE 2

This example illustrates the preparation of a compound of the formula

Into a 250 mL round bottom flask was added 5.33 grams of thetetralin-indan amine of Example 1 (3:1 ratio of two regio-isomers,C₁₉H₂₁N, M_(n)=263.38, 20.24 mmol, 1.00 eq.) under ambient condition.Next, 15 gram AgO (M_(n)=123.87, 242.19 mmol, 11.97 eq.) and 50 mLacetone were added to the flask. After 24 hours, the mixture wasfiltered to remove all solid and the residue solid was washed with 10 mLacetone. The solvent was removed via vacuum distillation to provide aproduct as a light brownish solid.

Formula: C₃₈H₄₀N₂, M_(n)=524.75

Yield: 5.1 gram, 96%

EXAMPLE 3 Preparation of Lubricating Oil Composition

To a motor oil formulation was blended 0.4 weight percent of thecompound of Example 2 and an additional 0.1 wt. % of Solvent Neutral 150base oil along with 50 ppm ferric naphthenate to form a lubricating oilcomposition. The motor oil formulation is set forth in Table 2.

TABLE 2 Motor Oil Formulation (Base Blend) wt % Solvent Neutral 15083.85 Zinc Dialkyldithiophosphate 1.01 Succinimide Dispersant 7.58Overbased Calcium Sulfonate Detergent 1.31 Neutral Calcium SulfonateDetergent 0.5 Antioxidant 0.0 Rust Inhibitor 0.1 Pour Point Depressant0.1 OCP VI Improver 5.55

COMPARATIVE EXAMPLE A Preparation of a Lubricating Oil Composition

To the motor oil formulation set forth in Table 2 was added anadditional 0.5 wt. % of Solvent Neutral 150 base oil along with 50 ppmferric naphthenate to form a lubricating oil composition.

Testing

The antioxidant properties of the lubricating oil composition of Example3 was evaluated and compared to the antioxidant properties of Naugalube438L (Nonylated diphenylamine, commercially available from ChemturaCorporation, Middlebury, Conn.) and the lubricating oil composition ofComparative Example A using the Pressurized Differential ScanningCalorimetry (PDSC) test and the Thermo-Oxidation Engine Oil SimulationTest (TEOST) as described below.

Pressurized Differential Scanning Calorimetry (PDSC)

The PDSC measures the relative oxidation induction time (OIT) ofantioxidants in a lubricating oil composition as measured in O₂ gasunder pressure. The PDSC instrument used is a Mettler DSC27HPmanufactured by Mettler-Toledo, Inc (Switzerland). The PDSC methodemploys a steel cell under constant oxygen pressure throughout each run.The instrument has a typical repeatability of ±2.5 minutes with 95percent confidence over an OIT of 100 minutes. The PDSC test conditionsare given in Table 35. At the beginning of a PDSC run, the steel cell ispressurized with oxygen and heated at a rate of 40° C. per minute to theprescribed isothermal temperature. The induction time is measured fromthe time the sample reaches its isothermal temperature until theenthalpy change is observed. The longer the oxidation induction time,the better the oxidation stability of the oil. The OIT results of thelubricating oil compositions of Example 3 and Comparative Example A andNaugalube 438L are set forth in Table 4.

TABLE 3 PDSC Test Conditions Test Parameters Settings Temperature 200°C. Gas Oxygen Flow Rate 100 mL/minute Pressure 500 psi Sample Size 1–5mg Pan (open/closed) open

TABLE 4 PDSC Results Ex./Comp. Ex. Time, minutes Example 3 18.7Naugalube 438L 16.7 Comp. Ex. A 4.5

It can be seen from the above data that a lubricating oil compositioncontaining the compound within the scope of the present inventionexhibited significantly better oxidative stability than a lubricatingoil composition containing no antioxidant. Mid-High TemperatureThermo-Oxidative Engine Oil Simulation Test

The Mid-High Temperature Thermo-oxidative Engine Oil Simulation Test(MHT TEOST) was performed to determine the deposit forming tendencies ofthe motor engine oil. The improved thermal deposit control of theadditives of this invention in stabilizing the engine oil formulationhas been clearly demonstrated by the MHT TEOST. This test determines themass of deposit formed on a specially constructed steel rod bycontinuously stressing a repetitive passage of 8.5 ml of test oil underthermal-oxidative and catalytic conditions. The instrument used wasmanufactured by Tannas Co. and has a typical repeatability of 0.15(x+16) mg wherein x is the mean of two or more repeated test results.The TEOST test conditions are listed in Table 5. The less the amount ofdeposits obtained, the better the oxidation stability of the oil. Theresults of this test are set forth in Table 6.

TABLE 5 TEOST MHT Test Conditions Test Parameters Settings Test duration24 hours Rod Temperature 285° C. Sample size 8.5 g (mixture of 8.4 g ofoil and 0.1 g of catalyst) Sample flow rate 0.25 g/min Flow rate (dryair) 10 mL/min Catalyst Oil soluble mixture containing Fe, Pb, and Sn

TABLE 6 TEOST Results Ex./Comp. Ex. mg deposits Example 3 35.5 Naugalube438L 71.2 Comp. Ex. A 108

It can be seen from the above data that the addition of a compoundwithin the scope of the present invention to a lubricating oilcomposition significantly reduces the total deposit mass of the baseblend formulation.

It will be understood that various modifications may be made to theembodiments disclosed herein. Therefore the above description should notbe construed as limiting, but merely as exemplifications of preferredembodiments. For example, the functions described above and implementedas the best mode for operating the present invention are forillustration purposes only. Other arrangements and methods may beimplemented by those skilled in the art without departing from the scopeand spirit of this invention. Moreover, those skilled in the art willenvision other modifications within the scope and spirit of the claimsappended hereto.

1. A tetraaromatic diamine compound having the general formula:

wherein a is 0-3; b, c and d independently are integers from 0-5, R¹ andR² together with the carbon atoms to which they are bonded are joinedtogether to form a substituted or unsubstituted C₃ to about C₃₀ ring,saturated, partially unsaturated or fully unsaturated, optionallysubstituted with one or more heteroatoms, R³, R⁴, R⁵ and R⁶ areindependently hydrogen, a straight or branched C₁-C₃₀ alkyl or alkylenegroup optionally substituted with one or more substituents, asubstituted or unsubstituted C₃-C₁₂ cycloalkyl, a substituted orunsubstituted C₅-C₂₅ aryl, a substituted or unsubstituted C₆-C₂₅arylalkyl, a straight or branched C₁-C₃₀ alkoxy group optionallysubstituted with one or more substituents or two R⁴ substituents and/ortwo R⁵ substituents and/or two R⁶ substituents on adjacent carbon atomsof the aromatic ring associated therewith can be joined together to forma substituted or unsubstituted C₃ to about C₃₀ ring, saturated,partially unsaturated or fully unsaturated, optionally substituted withone or more heteroatoms.
 2. The tetraaromatic diamine compound of claim1, wherein R¹ and R² are joined together to form a substituted orunsubstituted, saturated 5-, 6-, or 7-membered ring.
 3. Thetetraaromatic diamine compound of claim 1, wherein R¹ and R² are joinedtogether to form a substituted or unsubstituted, partially unsaturatedor fully unsaturated, 5-, 6-, or 7-membered ring.
 4. The tetraaromaticdiamine compound of claim 1, wherein two R⁴ substituents and two R⁵substituents and two R⁶ substituents on adjacent carbon atoms of thearomatic ring associated therewith are joined together to form asubstituted or unsubstituted C₃ to about C₃₀ ring.
 5. The tetraaromaticdiamine compound of claim 1, wherein two R⁴ substituents and two R⁵substituents and two R⁶ substituents on adjacent carbon atoms of thearomatic ring associated therewith are joined together to form asubstituted or unsubstituted, saturated 5-, 6-, or 7-membered ring. 6.The tetraaromatic diamine compound of claim 1, wherein two R⁴substituents and two R⁵ substituents and two R⁶ substituents on adjacentcarbon atoms of the aromatic ring associated therewith are joinedtogether to form a substituted or unsubstituted, partially unsaturatedor fully unsaturated 5-. 6-, or 7-membered ring.
 7. The tetraaromaticdiamine compound of claim 1, wherein R¹ and R² are joined together toform a substituted or unsubstituted and saturated, partially unsaturatedor fully unsaturated 5-, 6-, or 7-membered ring and two R⁴ substituentsand two R⁵ substituents and two R⁶ substituents on adjacent carbon atomsof the aromatic ring associated therewith are joined together to form asubstituted or unsubstituted and saturated, partially unsaturated orfully unsaturated 5-, 6-, or 7-membered ring.
 8. A lubricating oilcomposition comprising (a) at least one oil of lubricating viscosity and(b) an antioxidant improving effective amount of at least onetetraaromatic diamine compound having the general formula:

wherein a is 0-3; b, c and d independently are integers from 0-5, R¹ andR² together with the carbon atoms to which they are bonded are joinedtogether to form a substituted or unsubstituted C₃ to about C₃₀ ring,saturated, partially unsaturated or fully unsaturated, optionallysubstituted with one or more heteroatoms, R³, R⁴, R⁵ and R⁶ areindependently hydrogen, a straight or branched C₁-C₃₀ alkyl or alkylenegroup optionally substituted with one or more substituents, asubstituted or unsubstituted C₃-C₁₂ cycloalkyl, a substituted orunsubstituted C₅-C₂₅ aryl, a substituted or unsubstituted C₆-C₂₅arylalkyl, a straight or branched C₁-C₃₀ alkoxy group optionallysubstituted with one or more substituents or two R⁴ substituents and/ortwo R⁵ substituents and/or two R⁶ substituents on adjacent carbon atomsof the aromatic ring associated therewith can be joined together to forma substituted or unsubstituted C₃ to about C₃₀ ring, saturated,partially unsaturated or fully unsaturated, optionally substituted withone or more heteroatoms.
 9. The lubricating oil composition of claim 8,wherein in the tetraaromatic diamine compound R¹ and R² are joinedtogether to form a substituted or unsubstituted, saturated 5-, 6-, or7-membered ring.
 10. The lubricating oil composition of claim 8, whereinin the tetraaromatic diamine compound R¹ and R² are joined together toform a substituted or unsubstituted, partially unsaturated or fullyunsaturated 5-, 6-, or 7-membered ring.
 11. The lubricating oilcomposition of claim 8, wherein in the tetraaromatic diamine compoundthe two R⁴ substituents and two R⁵ substituents and two R⁶ substituentson adjacent carbon atoms of the aromatic ring associated therewith arejoined together to form a substituted or unsubstituted C₃ to about C₃₀ring.
 12. The lubricating oil composition of claim 8, wherein in thetetraaromatic diamine compound R¹ and R² are joined together to form asubstituted or unsubstituted and saturated, partially unsaturated orfully unsaturated 5-, 6-, or 7-membered ring and two R⁴ substituents andtwo R⁵ substituents and two R⁶ substituents on adjacent carbon atoms ofthe aromatic ring associated therewith are joined together to form asubstituted or unsubstituted and saturated, partially unsaturated orfully unsaturated 5-, 6-, or 7-membered ring.
 13. The lubricating oilcomposition of claim 8, wherein the at least one oil of lubricatingviscosity is selected from the group consisting of engine oils,transmission fluids, hydraulic fluids, gear oils, marine cylinder oils,compressor oils, refrigeration lubricants and mixtures thereof.
 14. Thelubricating oil composition of claim 8, further comprising at least onelubricating oil additive selected from the group consisting ofantioxidants, anti-wear agents, detergents, rust inhibitors, dehazingagents, demulsifying agents, metal deactivating agents, frictionmodifiers, pour point depressants, antifoaming agents, co-solvents,package compatibilisers, corrosion-inhibitors, ashless dispersants,dyes, extreme pressure agents and mixtures thereof.
 15. The lubricatingoil composition of claim 8, further comprising at least one lubricatingoil additive selected from the group consisting of an alkylateddiphenylamine, alkylated hindered phenolic, alkylated substituted orunsubstituted phenylenediamine, alkylated oil soluble copper compound,alkylated sulfur containing compound known to impart oxidation stabilityand mixtures thereof.
 16. The lubricating oil composition of claim 15,wherein the alkylated sulfur containing compound known to impartoxidation stability is selected from the group consisting ofphenothiazines, sulfurized olefins, thiocarbamates, sulfur bearinghindered phenolics, zinc dialkyldithiophosphates and mixtures thereof.17. The lubricating oil composition of claim 8, having a phosphorouscontent of less than about 0.1 weight percent.
 18. An additive packagecomprising about 1 to about 75 weight of at least one tetraaromaticdiamine compound of claim
 1. 19. A stabilizer-containing compositioncomprising (a) an organic material subject to oxidative, thermal, and/orlight-induced degradation and in need of stabilization to prevent orinhibit such degradation; and (b) a stabilization effective amount of atleast one tetraaromatic diamine compound of claim
 1. 20. A method forstabilizing an organic material subject to oxidative, thermal, and/orlight-induced degradation and in need of stabilization to prevent orinhibit such degradation, the method comprising adding to the organicmaterial a stabilizing amount of at least one tetraaromatic diaminecompound of claim 1.